The present invention generally relates to driveline power transfer mechanisms and more particularly, to driveline power transfer mechanisms that include a cooling system.
Modern vehicles typically include an axle assembly having a housing and a differential assembly. The housing includes a cavity into which the differential assembly is rotatably disposed. The differential assembly is mechanically coupled to the vehicle's engine by a drive shaft. The differential assembly is also coupled to the vehicle drive wheels via a pair of axle shafts. The differential assembly regulates the drive torque between the axle shafts thereby causing the shafts to rotate. During operation of the vehicle, friction between the various components of the differential assembly generates heat, which if unabated could decrease the useful life of the axle assembly. A lubricating fluid, which is contained within the cavity of the axle assembly is therefore typically employed to remove heat from the various components of the differential assembly. The lubricating fluid then rejects, or transfers, this heat to the housing, which, in turn, rejects or transfers this heat via convection, conduction, and radiation to the environment in which the vehicle is operating.
Current advances in the fuel efficiency of vehicles have resulted in decreased air flow under the vehicle, which significantly reduces the capability of the housing of the axle assembly to reject heat.
One solution that has been suggested utilizes a dedicated heat exchanger for removing heat from the housing of the axle assembly. Several drawbacks have been noted with this approach, however. For example, the viscosity of the lubricating fluids in an axle assembly is such that the lubricating fluid is relatively difficult to pump, particularly when the ambient air temperature is relatively low. Another drawback concerns the cost of the pumps and heat exchangers used in these systems.
In view of the aforementioned drawbacks, there remains a need in the art for an axle assembly having a cooling system that provides improved cooling of the axle lubricant and axle assembly components.